xlr outs plugged into my mbox when not in protools....

dpeterson

Axe-Master
makes the axe-fx sound like ass. It was a distorted sound, kind of like a farting sound... unplugged the xlr's and it was back to normal.

anyone else experience this?

dave
 
Most likely your Mbox XLR inputs are Mic level while AFX XLR out is +4 pro line level. This kind of level is way too hot for the mic inputs. I would suggest using either 1/4 line inputs if you have any or XLR to TRS adapter of course if your Mbox have TRS balanced input. TRS inputs are usually designed with a line level application in mind and should handle hotter signals much better.

Mik.
 
hmm i dont think i was clear enough..

i have the xlrs going into the mbox fine.. no distortion, i can record, everything is golden.

i turn off my computer, axe sounds horrible... reach around and unplugh the xlrs from the back, and it sounds fine.
 
This happens because the Mbox is loading down the outputs when not powered. This is quite common when using a non-inverting op-amp configuration as an input buffer. The correct solution is to unplug the cables to the mbox.

CC
 
FractalAudio said:
This happens because the Mbox is loading down the outputs when not powered. This is quite common when using a non-inverting op-amp configuration as an input buffer. The correct solution is to unplug the cables to the mbox.

CC

Sorry but I only got the last sentence. What does "loading down" mean?
 
jdawgesq said:
Sorry but I only got the last sentence. What does "loading down" mean?
It means that, when the device is turned off, its inputs present very low impedances to any device that is connected to them, thus loading those outputs to the point that they do not function properly. This is a very common occurrence, and it is never good practice to leave operating outputs connected to the inputs of a device that is not powered up.
 
This happens usually because the designer left off the isolation resistor. Technically you don't need one but this is what happens when you leave it out. Yeah, you save 2 cents but you risk damaging the op-amp from both unpowered drive situations and ESD discharge as there's no current limiting. Also, I've found the isolation resistor helps prevent high-frequency noise pickup by forming a gentle low-pass with the input capacitance.
 
Does anyone know whether this is an Mbox-only issue or are Digi 002s and 003s built the same way?

Unplugging XLRs every single time I turn off my interface isn't the end of the world, but it would be a definite plus if didn't have to.
 
well i'm not going to buy a whole new system just because of that. It is inconvienent, i'm not sure about the other digidesign stuff. I have a panel that has the xlr's on it on the back of my rack, so it's easy enough to uplug..
 
dpeterson said:
well i'm not going to buy a whole new system just because of that. It is inconvienent, i'm not sure about the other digidesign stuff. I have a panel that has the xlr's on it on the back of my rack, so it's easy enough to uplug..

Agreed I did not spend the time to learn Pro Tools to buy a different device. Unplug seems to be the best solution.
 
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